This invention involves a procedure to improve visual acuity of individuals having subnormal vision and suffering from significant focusing impairment, usually severe myopia. More particularly, it involves a procedure which includes a specially designed graphic for testing visual acuity used for arriving at a best estimate for ocular correction and a prescription for soft contact lenses to be used with a plurality of spectacle lenses for training and determining the patient's optimal correction.
The human eye comprises a lens through which light enters and is focused on nerve endings in the retina to produce a definite mental picture. Muscles direct eyes towards objects to be observed, position their lenses relative to the retina and control the curvature of each lens. The nerve endings of the retina comprise light-sensitive rods and cone cells. Cone cells are responsible for color vision and for detailed vision at the center of the visual field known as the fovea centralis. Although rod cells provide only black and white vision and less detailed information, they are considered much more sensitive at low intensity illumination.
Many people are born with a severe retina damage, having gross scarring, atrophy or irregularities of their retina. Retina damage may be also acquired after birth. In either case, an individual suffering from retina damage may have as little as five to ten percent of his or her operative retina intact in both eyes or in one eye with the other eye worse or completely blind. Such individuals are a challenge to ophthalmologists and optometrists, particularly for ophthalmologists and optometrists who specialize with the treatment of subnormal and low vision patients.
Most patients with low vision are prescribed corrective lenses that give maximum strength at the time of their initial examination. For a number of years, they were taught to "save" their eyes to conserve vision. However they are now advised to use their eyes. Deceptive publicity has occurred from time to time on certain optical aids which has had a tendency to give partial seeing patients false hopes. Because of this and because there is no present means known to restore permanently damaged receptors in the retina, patients have been encouraged to live with their handicap and limit their activities accordingly.
It is known that subnormal vision can be corrected in certain instances with contact lenses. However, such improvement has been limited--usually not more than one line of an eye chart. Nevertheless, the degree of magnification in myopia is much greater with contact lenses. It was noted in Management of the Patient with Subnormal Vision by G. Fonda published by the C.V. Mosby Company, St. Louis, 1970, that low vision patients do not seem to appreciate the improved visual field contact lenses provide as much as would be expected.
The low vision patient must bring his eyes close to the subject matter to read and for many activities such as eating. For such patient, the outside world is extremely blurred. This contrasts, interestingly, with the patient's ability to see photographs and television images if sufficiently close to same. To test vision between 20/200 and 20/100 special eye charts are recommended such as the Bausch & Lomb charts 71-35-93 and H-356 and the Sloan letters AOC 11076 project O-Chart. Test types larger than 20/200 have been considered unnecessary because available charts can be used at distances less than twenty feet such as, for example, five feet or less from the patient. A problem with charts in general has been that they are almost always black on white, comprise letters or similar abstract figures and the low vision patient is inclined to make guesses (often accurate) of the letters. It has thus been considered difficult to make accurate eye tests with patients having low vision. Success is often equated with providing the patient with prescriptive lenses which are sufficient to enable the patient to read. This is true although correction of subnormal vision is usually made for both distant and near vision.
There are a number of United States patents which relate to special vision charts and methods of using same for eye exercises. These included U.S. Pat. No. 1,780,291 of Nov. 4, 1930, to A. Cameron which relates to an optical apparatus for testing and charting visual and color fields of a patient's eyes; U.S. Pat. No. 1,990,218 of Feb. 5, 1935, to G. Bailey which is directed to means for determining acuteness of perception on the part of patients for the use of models which may be manipulated; U.S. Pat. No. 2,196,904 of Apr. 9, 1940, to R. Sherman and U.S. Pat. No. 2,387,442 of Oct. 23, 1945, to G. Hamilton relate to devices for testing visual acuity and for visual training which involve the use of stereoscopic devices; U.S. Pat. No. 2,781,042 of Feb. 12, 1957, to J. Bartow discloses a device for testing stereoscopic vision wherein a moving model is employed; U.S. Pat. No. 3,244,468 of Apr. 5, 1968 to R. Meltzner discloses a diorama which is used for testing visual acuity with three dimensional scenic representations; U.S. Pat. No. 3,842,822 of Oct. 22, 1974 and U.S. Pat. No. 3,955,565 of May 11, 1976 to H. Levinson et al relate to dysmetric dyslexia screening procedures and method of improving occular fixation, sequential scanning and reading activity in dysmetric dyslexic children; U.S. Pat. No. 3,910,690 of D. Regan of Oct. 7, 1975, which relates to apparatus for measuring visual acuities in different retinal areas of the patient; U.S. Pat. No. 3,986,500 to H. Tsuruta of Oct. 19, 1976, which discloses therapeutic treatment for myopia by a repetition of focusing and staring alternatively at a distant object and a nearby object and a visual acuity chart; U.S. Pat. No. 4,365,873 to A. Ginsburg of Dec. 28, 1982, which discloses a visual chart and method of using same to evaluate the visual and optical systems of patients undergoing analysis in terms of both contrast sensitivity and spatial frequency response.